1. Field of the Invention
The present invention relates to the field of micro-injecting devices and methods of a manufacturing the same.
2. Description of the Related Art
Generally, the term micro-injecting device refers to a device which is designed to provide printing paper, a human body or motor vehicles with a predetermined amount of liquid, for example, ink, injection liquid or petroleum using the method in which a predetermined amount of electric or thermal energy is applied to the above-mentioned liquid, yielding a volumetric transformation of the liquid. This method allows the application of a small quantity of a liquid to a specific object.
Recently, developments in electrical and electronic technology have enabled rapid development of such micro-injecting devices. Thus, micro-injecting devices are being widely used in daily life. One example of the use of micro-injecting devices in daily life is the inkjet printer.
The inkjet printer is a form of micro-injecting device which differs from conventional dot printers in the capability of performing print jobs in various colors by using cartridges. An additional advantage of inkjet printers over dot printers is the fine, clear letters produced on paper by the ink-jet printer. As a result, the use of inkjet printers is increasing.
An inkjet printer generally includes a micro-injecting device having nozzles with a minute diameter. The micro-injecting device discharges ink by transforming the liquid ink and expanding the ink to an air bubble according to electric signals from outside the printer, and thereby carries out the printing of letters and images on paper.
Examples of the construction and operation of several ink jet print heads of the conventional are seen in the following U.S. patents. U.S. Pat. No. 4,490,728, to Vaught et al., entitled Thermal Ink Jet Printer, describes a basic print head. U.S. Pat. No. 4,809,428, to Aden et al., entitled The Film Device For An Ink Jet Printhead and Process For Manufacturing Same and U.S. Pat. No. 5,140,345, to Komuro, entitled Method Of Manufacturing a Substrate For A Liquid Jet Recording Head And Substrate Manufactured By the Method, describe manufacturing methods for ink-jet printheads. U.S. Pat. No. 5,274,400, to Johnson et al., entitled Ink Path Geometry For High Temperature Operation Of Ink-Jet Printheads, describes altering the dimensions of the ink-jet feed channel to provide fluidic drag. U.S. Pat. No. 5,420,627, Keefe et al, entitled Ink Jet Printhead, shows a particular printhead design.
Generally, the micro-injecting device uses a high temperature generated by a heating resistor layer to discharge the ink on the paper. Accordingly, the high temperature which is generated by the heating resistor layer has an effect on ink contained in a liquid chamber for a long time. As a result, the ink is thermally transformed and this causes a decrease in the durability of an apparatus containing the ink.
Recently, to overcome this problem, there has been proposed a new method for smoothly spraying ink from the ink chamber toward the outside by disposing a plate membrane between the heating resistor layer and the ink chamber and inducing a dynamic deformation of the membrane under a pressure of a working fluid, for example, heptane. Since the membrane is disposed between the ink chamber and the heating layer, preventing the ink from contacting directly to the heating layer, the ink itself is subjected to little thermal transformation. An example of this type of printhead is seen in U.S. Pat. No. 4,480,259, to Kruger et al., entitled Ink Jet Printer With Bubble Driven Flexible Membrane.
In conventional membrane-containing micro-injecting devices, both ink and a working liquid are usually used in printing the letters and images. Therefore, separate chambers must be provided in the micro-injecting device to store the ink and the working liquid.
For this purpose, the micro-injecting device has a liquid chamber barrier layer and a heating chamber barrier layer formed in the device, which respectively define the chambers. The chambers contain the ink and the working liquid reliably.
Generally, the ink chamber barrier layer and the heating chamber layer are each more than 10 .mu.m thick (deep) so that each chamber has sufficient volume. Organic materials are used as raw materials for both the ink and the working liquid for reasons of chemical compatibility.
As described above, since the chambers which are defined by the ink chamber barrier layer and the heating chamber layer must contain chemicals such as the ink and the working liquid, the chambers must have a high corrosion-resistance. The heating chamber barrier layer and the ink chamber barrier layer are corroded by the chemical when the chemical stays in the chambers for a long time. Accordingly, the heating chamber barrier layer and the ink chamber barrier layer may form gaps at boundaries between these layers and the nozzle plate or the membrane of the device.
In this case, the chemical which is contained in the chambers leaks from the chambers to construction which are not resistant to the chemical. The leakage of the chemical results in markedly degrading the general durability of the micro-injecting device.
Of note is the disclosure of U.S. Pat. No. 5,417,835, to Brown et al., entitled Solid State Ion Sensor With Polyimide Membrane, which discloses a sensor using a polyimide matrix membrane. In this membrane-containing device, which is quite different from a micro-injecting device, the membrane is made of polyimide, taking advantage of the excellent adherence characteristics of polyimide.
Also of note is a new method for preventing the leakage of the ink or the working liquid proposed to overcome the above problem U.S. Pat. No. 5,198,834, to Childers et al., entitled Ink Jet Print Head Having Two Cured Photoimaged Barrier Layers, discloses a method of preventing a leakage of an ink which is contained in ink chambers. According to this patent, a barrier wall include two layers, one layer a negatively acting photoimageable soldermask the second negatively acting lithographic photoresist. The second material is applied to adhesively couple the first layer to the orifice plate above. Thus the second layer serves as a progressive layer between the first, or base, layer and the orifice plate. As the attachment of the ink chamber barrier layer and a nozzle plate is improved by attaching the progressive layer of the ink chamber barrier layer to the nozzle plate, formation of a gap between the ink chamber barrier layer and the nozzle plate is prevented. The patent describes a first layer made of an epoxy acrylate and a second layer made of Waycoat SC is resist 900.
In this case, however, there is a disadvantage in that the number of processing steps is increased since the ink chamber barrier layer is comprised of two layers, the base layer and the progressive layer. Furthermore, when the ink chamber barrier layer is attached to the nozzle plate, the progressive layer inhibits the aligning of the ink chamber barrier layer and the nozzle plate. Accordingly, there is a problem in that the ink camber barrier layer may be not properly attached to the nozzle plate.
If the ink chamber barrier layer is not aligned to the nozzle plate, a misalignment may occur between the ink chamber barrier layer and the nozzle plate. Accordingly, a passageway for the ink may be partially obstructed by a disorder. That causes the ink not to be smoothly discharged. At a result, the printing performance of the ink jet printer head is markedly degraded.